Hard disk drives (HDDs) require a certain amount of cooling for efficient and reliable operation over a long life. When a single drive is installed in a drive enclosure (FIG. 1), heat which is generated may be dissipated through convection or mechanically with a cooling fan. The industry has been moving towards disk drive modules (DDMs) with a smaller form factor which require less volume than their predecessors. Thus, high density packaging of multiple smaller drives within a single enclosure or service boundary is a more efficient use of space than standard rack mounted drives. In FIG. 2, sixteen DDMs, each holding, for example, a 3.5 inch drive, are installed one-deep in a single enclosure. A cooling fan or blower directs air through the enclosure from front to back (or back to front) in the direction of the arrow. Thus, each DDM is the same distance from the fan as each other DDM and each, therefore, receives the same cooling effect from the airflow.
As drive density continues to increase, small form factor 2.5 inch drives are being used. However, one-deep packaging of 2.5 inch drives is not an efficient use of volume and multi-drive trays (MDTs) have been developed in which two or more small HDDs are installed from front to back in an enclosure. The same cooling airflow remains in use with such MDTs. Therefore, the first HDD in the airflow (that is, the HDD closest to the source of the airflow) will be exposed to the coolest air and will heat the air as it flows past. The last HDD in the airflow (that is, the HDD farthest from the airflow source) will be exposed to the warmest air. Because HDD reliability is related to the operating temperature, those drives farthest from the airflow source will tend to have the lowest reliability and/or shortest life.
Consequently, there remains a desire to reduce the uneven effects of a cooling airflow on HDDs in an MDT.